How to avoid "Sign in to iTunes" popup on every app launch

### Platform

- [x] iOS

### In app purchase type

- [x] Non-consumable
- [x] Auto-Renewable Subscription

### Environment

- [x] Sandbox

### Version

0.13.3

## Report

### Issue summary

I'm only allowing users to access the app after they buy a subscription. To make sure that the auto-renewable subscription is still active I call `SwiftyStoreKit.verifyReceipt` and `SwiftyStoreKit.verifySubscriptions` to receive all the receipts and check the expiration date every time the app is launched. Calling those methods causes "Sign In To iTunes Store" pop-up appear every time.

Is there a good way to avoid those popups while still being able to verify that the subscription is still active on each app launch?

One possible solution would be for me to keep the receipts on my own backend and verify them first instead of going straight to iTunes Store. Is that what everyone is doing?